1. Field of the Invention
The present invention relates to advection fans and, more particularly, to advection fans that allow air currents to enter and exit in a direction perpendicular to an axial direction.
2. Description of the Related Art
Conventional cooling fans generally include axial fans and blower fans. An axial fan generally includes an axial air inlet and an axial air outlet spaced in an axial direction. Air currents are guided into the axial air inlet and then exit from the axial air outlet to provide a cooling function. A blower fan generally includes an axial air inlet and a radial air outlet. Air currents are guided into the axial air inlet and then exit from the radial air outlet to provide the cooling function.
However, axial fans can only guide air currents to flow in the axial direction for cooling purposes. Namely, axial fans can not guide air currents to flow in the radial direction. Thus, the axial fans must be mounted on top of a heat source (such as on a top face of a central processing unit of a personal computer) when used in various electronic products, such that the overall axial height of the electronic products can not be reduced. Although blower fans can guide air currents to exit from the radial air outlet, the air currents must be guided into the blower fans via the axial air inlet. As a result, the blower fans are not suitable for electronic products (such as cell phones, personal digital assistants, etc,) that must guide the air currents in lateral direction into a lateral side of the electronic product.
Namely, axial fans and blower fans currently available in the market can not be applied in small electronic products having limited inner spaces.
Taiwan Patent Publication No. 553323 discloses an advection fan that guides air currents in and out in a radial direction. Such an advection fan is more suitable for small electronic products that guide the air currents into the lateral side.
FIG. 1 shows another advection fan 9 including a housing 91 and an impeller 92. The housing 91 includes an air passage 911 receiving a stator 93. The stator 93 includes a shaft seat 931, silicon steel plates 932 mounted around the shaft seat 931, coils 933, and insulating bobbins 934. The impeller 92 is rotatably coupled to the shaft seat 931. The stator 93 drives the impeller 92 to rotate to drive air currents to enter an end of the passage 911 and exit from the other end of the passage 911, providing a cooling function.
The advection fan 9 is used in small electronic products and is miniaturized in the volume and the axial height of the housing 91. However, the passage 911 must receive the stator 93 that includes the silicon steel plates 932, the coils 933, and the insulating bobbins 934 and, thus, occupies a considerable space in the passage 911. The air guiding space in the miniaturized housing 91 is insufficient for guiding air currents, leading to a significant decrease in the air output and the wind pressure. Furthermore, unnecessary noise could occur due to hindrance to the air currents by the silicon steel plates 932, the coils 933, and the insulating bobbins 934. Further, the housing 91 must include a predetermined axial height “H” to provide sufficient room for receiving the stator 93. As a result, the volume and the axial height “H” of the housing 91 for receiving the stator 93 can not be further reduced while assuring sufficient space for guiding air currents. Namely, development and research in miniaturization of the advection fan 9 of this type is impossible. Further, the impeller 92 mounted in the passage 911 must be in the form of a hub to receive the stator 93. Thus, the air currents are hindered by a large portion of the hub while flowing through the passage 911, causing turbulence and resulting in considerable insufficiency in the air output and the wind pressure, significantly and adversely affecting the overall cooling effect of the advection fan 9.